1. Field of the Invention
The present invention relates to a map display apparatus and, more particularly, to a display apparatus which can properly display both of a wide area map and an enlarged map in which a part of the wide area map is displayed in an enlarged state.
2. Description of Background Information
In recent years, there have been developed various systems in which a display unit is mounted in a vehicle as one of equipments used in a vehicle, map data is stored in a storage medium such as a CD-ROM or the like, a group of map data of a desired area is read out from the storage medium by a reading apparatus and is supplied as a display information signal to the display unit, thereby displaying a map onto the display and so that the present location of the vehicle can be confirmed by viewing the displayed map.
Together with the wide area map data group corresponding to a certain wide area, a plurality of divisional map data groups corresponding to a plurality of divided areas which are obtained by dividing the wide area are stored in the storage medium such as a CD-ROM. Therefore, for displaying a map, the wide area can be properly displayed by a wide area map of a small reduction ratio, while one of the plurality of divided areas can be properly displayed by an enlarged map of a large reduction ratio, by reading out necessary map data groups from the CD-ROM and supplying the map data groups as a display information signal to the display.
For instance, a cursor frame C is displayed into a certain area (one of the plurality of divided areas) on the display screen of the wide area map by a key entry of a cursor key as shown in FIG. 7A and a command to display the enlarged map is generated by a key entry. Through these operations the divided area designated by the cursor frame C is displayed as an enlarged map as shown in FIG. 7B. The display state can be brought back from the enlarged map to the original wide area map by generating a command for displaying the wide area map in response to a key entry under the condition of displaying the enlarged map mentioned above.
According to the conventional display method, when what is called a wide area process such as a process for bringing back the display state from the enlarged map to the original wide area map is performed, the cursor frame C is displayed at the center of the wide area map screen as shown in FIG. 7C. Therefore, an inconvenience has been experienced such that the position of the divided area on the wide area map screen corresponding to the enlarged map which has been displayed just before the wide are process is executed cannot be known, so that such a position must be determined relying on the user's memory.